Pathways to Self-Assembly of Ultra-Narrow Size Distributions of Heteroepitaxial Semiconductor Quantum Dots

9804310德鲁克这个项目致力于异质外延半导体相干岛量子点的自组装。方法是研究Ge/Si(100)系统中自组装的原子机制；尽管Ge/Si(100)是已观察到的最简单的自组装系统，但它保留了在更复杂的合金半导体系统中观察到的许多与自组装相关的行为，如SiGe/Si，InGaAs/GaAs。各种原位和非原位显微镜(扫描隧道显微镜、原子力显微镜和扫描和透射电子显微镜)将被用来表征由分子束外延(MBE)和化学气相沉积(CVD)形成的自组装量子点(SAQD)。为了确定在整个SAQD系统中获得所需尺寸和形状均匀度的途径，我们将系统地研究可通过实验获得的参数的相空间：衬底温度、沉积速率、总覆盖率和生长后的退火。主要目标是在保持灵活性的同时获得这种一致性，以改变不同样品的网点大小分布的平均半径和网点的面密度。利用光致发光光谱，观测到的Ge/Si(100)SAQD的形貌将与其光学性质相关联。作为实验研究的补充，将进一步发展应变岛系统中微结构演化的模型。该模型考虑了相干海岛的弹性能和远离应变海岛的扩散偏向，该扩散偏向随着海岛尺寸的增大而增大。通过应变岛生长的动力学蒙特卡罗模拟，将进一步深入了解自组装过程。%该项目致力于具有高度技术相关性的材料科学主题领域的基础研究问题。这项研究将在基础水平上为电子/光子器件的重要方面贡献基本的材料科学知识。现在可以使用实验工具对基本过程进行原子水平的观察，如果更好地理解，这将促进基础科学和技术的进步。从研究中获得的基本知识和理解有望为设计和生产改进的材料和材料组合提供基本的理解和基础，从而有助于提高先进器件和电路的性能和稳定性。该计划的一个重要特点是通过在一个具有根本意义和技术意义的领域对学生进行培训，将研究和教育结合起来。***

9804310 Drucker This project addresses self-assembly of heteroepitaxial semiconductor coherent island quantum dots. The approach is to study atomistic mechanisms of self-assembly in the Ge/Si(100) system; since, although Ge/Si(100) is the simplest system for which self-assembly has been observed, it retains much of the self-assembly related behavior observed in more complex alloy semiconductor systems such as SiGe/Si, InGaAs/GaAs. A variety of in and ex situ microscopies (scanning tunneling, atomic force and scanning and transmission electron microscopies) will be employed to characterize ensembles of self-assembled quantum dots (SAQD) formed using molecular beam epitaxy (MBE) and chemical vapor deposition (CVD). The phase-space of experimentally accessible parameters; substrate temperature, deposition rate, total coverage and postgrowth annealing, will be systematically investigated in order to identify pathways to obtaining desired size and shape uniformity throughout the ensemble of SAQD. A primary goal is to obtain this uniformity while retaining the flexibility for varying the mean radius of the dot size distribution and the areal density of the dots from sample to sample. The observed morphology of the Ge/Si(100) SAQD will be correlated with their optical properties using photoluminescence spectroscopy. The experimental investigations will be complemented by further development of a model of microstructural evolution in strained island systems. This model incorporates the elastic energy of coherent islands and a diffusion bias away from strained islands which increases with island size. Further insight into the self-assembly process will be gained through kinetic Monte Carlo simulations of strained island growth. %%% The project addresses basic research issues in a topical area of materials science having high technological relevance. The research will contribute basic materials science knowledge at a fundamental level to important aspects of electroni c/photonic devices. Experimental tools are now available to allow atomic level observation of elementary processes which when better understood will allow advances in both fundamental science and technology. The basic knowledge and understanding gained from the research is expected to contribute to improving the performance and stability of advanced devices and circuits by providing a fundamental understanding and a basis for designing and producing improved materials, and materials combinations. An important feature of the program is the integration of research and education through the training of students in a fundamentally and technologically significant area. ***